A Bio-IA With Fast Recovery and Constant Bandwidth for Wearable Bio-Sensors

This paper proposes a bio-signal instrumentation amplifier (Bio-IA) with fast recovery and constant bandwidth for wearable bio-sensors. To shorten the offset calibration time of the Bio-IA and reduce the loss of bio-signal in the calibration process, a digital-controlled DC servo loop (DCDSL) with fast recovery is designed, which achieves a larger offset calibration range and a faster calibration speed. The proposed programmable gain amplifier (PGA) with constant bandwidth uses dual-biased pseudo-resistor (PR) to stabilize the passband width under different gains, effectively preventing the loss of low-frequency signals. Besides, this paper analyzes the noise of the DCDSL and the noise of dual-biased PR for the first time. The presented Bio-IA was implemented in a 0.18- μm CMOS process, occupying a core area of 849 μm×451 μm. The measured results show that the Bio-IA can calibrate a DC offset of ±511 mV, and the response time is less than 70 ms when the offset polarity changes suddenly. When the gain of the Bio-IA varies from 26 to 40 dB, its passband width remains constant, and the high-pass and low-pass cut-off frequencies are 0.4 Hz and 200 Hz, respectively. The input-referred noise over the range of 0.1-200 Hz is 0.72 μVrms. The proposed Bio-IA consumes 5.5 μW from 1.2 V supply voltage.